1. Field of the Invention
The present invention relates to an electrochemical device and a method for manufacturing this device, and more particularly relates to an electrochemical device having a structure in which separators are alternately laminated with collectors each having a polarizable electrode layer formed on their surface, and to a method for manufacturing this device. The present invention also relates to an electrochemical device manufacturing jig, and more particularly to an electrochemical device manufacturing jig for positioning and alternately laminating collectors and separators.
2. Description of the Related Art
Electrochemical devices such as electric double-layer capacitors have been attracting attention in recent years as batteries that are compact and lightweight and have a relatively large capacity. Electric double-layer capacitors are a type of battery that stores electrical charges directly in electrodes, rather than utilizing a chemical reaction as is the case with ordinary secondary cells, and therefore have the advantage that they can be charged and discharged extremely quickly. This feature holds promise for applications such as backup power sources for portable devices (small electronic devices) and so forth, auxiliary power sources for electric and hybrid vehicles, and so on, and a great deal of research has gone into improving the performance of these capacitors.
The basic structure of an electric double-layer capacitor comprises a plurality of collectors on which a polarizable electrode layer has been formed, alternately laminated with a plurality of separators that separate adjacent polarizable electrode layers. The inside of these collectors is filled with an electrolytic solution. If any misalignment in the lamination position should occur in the lamination of the collectors and separators, the completed integrated body will have a distorted shape, and in some cases problems such as shorting between the positive and negative electrodes can occur, so the lamination must be performed in the proper positions. Therefore, techniques such as image recognition have been used in the past to control the lamination positions.
However, positioning by image recognition not only makes such control more complicated, it also reduces work efficiency. In response to this, Japanese Laid-Open Patent Application 2001-93508 discloses a method in which the lamination positions are controlled by providing positioning through-holes to the positive and negative. electrode plates, and laminating while inserting positioning pins into these through-holes.
As a result of investigation into the method described in Japanese Laid-Open Patent Application 2001-93508, the present inventors discovered that not only is it necessary to form bag-shaped separators ahead of time on the positive or negative electrode plates, but it is also necessary to accurately control the positions where these bag-shaped separators are formed, which is a problem in that production efficiency is low.
Furthermore, a property of an electric double-layer capacitor in which a carbonaceous material or the like is used as the material for a polarizable electrode layer is that the polarizable electrode layer expands by about 10% in its thickness direction during charging. When this expansion occurs, not only does it apply stress to the housing by deformation, but it also increases the internal stress of the electric double-layer capacitor. Consequently, it is necessary to provide a pair of integration fixing plates or the like in the lamination direction of the integrated body that will serve as the capacitor main body, and thereby suppress expansion. Nevertheless, the inventors have discovered that it is difficult to suppress expansion in the center portion after positive and negative electrode plates have been laminated by the method described in Japanese Laid-Open Patent Application 2001-93508.